Booming demand for mobile storage and data center solid state drives is helping memory makers. Hard drive makers are benefiting indirectly for now, but they have reasons to be nervous.

Life is very good for NAND flash memory makers right now. That's ultimately a positive for the DRAM industry as well. The hard drive industry, on the other hand, might have mixed feelings.

Toshiba, the world's second-biggest NAND supplier after Samsung and a long-time manufacturing partner of Western Digital's (WDC) recently-acquired SanDisk unit, has hiked its operating profit forecast for the fiscal year ending in March to about $1.7 billion. Not surprisingly, the company cited strong NAND demand, and added that market conditions are expected to remain favorable for the rest of the fiscal year.

This comes after Western beat its calendar Q3 estimates -- the company had already hiked its guidance for the quarter in September -- and issued above-consensus Q4 guidance, while reporting it's seeing very strong flash demand. The company also forecast on its earnings call NAND industry bit production will grow by about 45% next year, better than 2016's estimated 35% growth.

Before that, DRAM and NAND maker Micron (MU) beat August quarter estimates and offered above-consensus guidance. The company is benefiting from both improving DRAM and NAND demand, and forecasts long-term annual NAND bit demand growth will be in the low-40s range.

Industry data also points to burgeoning NAND demand. In October, prices for 64-gigabit (8GB) multi-level cell (MLC) NAND chips topped $3 for the first time in two years. Such a surge is unusual, as manufacturing process advances improve memory densities and lower per-gigabit production costs over time.